The present apparatus is directed to a flex or knuckle joint which can be incorporated in an oil tool adapted to be lowered in a well borehole. Moreover, this is intended for incorporation in a long well tool which require midpoint flexure or bending. Indeed, it is not uncommon to require more than one flexure joint. Two or three joints may be necessary to enable a very long tool to travel along a serpentine passage as might typically be encountered in well completion services, conducting logging operations and the like.
The problem of bending a tool is not new; knuckle joints have been devised heretofore which enable long weight strings to be attached beneath a tool, the system typically including a sphere serving as an enlargement which is locked by a surrounding collar which has a certain measure of play. The present apparatus goes far beyond that in that it is intended for a knuckle or flexure joint which encloses multiple conductors along the center of the equipment. A sealed system is provided wherein the conductors are enclosed in an internal passage. The passage has sufficient size to receive multiple cables therein which are protected against the intrusion of well bore fluids. The interior is thus a sealed oil bath in which the conductors and the components of the system are pressure isolated from invasion of fluids common to the well. The pressure is maintained at the control level by incorporating a compensating piston which is exposed to prevailing pressures in the well borehole. The compensating piston bears against the oil bath to assure that the oil bath is properly pressurized, and moreover to ensure compensation for changes in oil volume due to compression of the fluid or other changes in volume. The compensating piston is spring loaded on the side of the well bore fluid to provide a positive pressure on the captured oil bath. The oil bath in conjunction with the constant pressure applied to it thus assuredly excludes well fluid from the interior working components of the system. This particularly protects the conductors and enables them to flex. Moreover, knotting, pinching or twisting of the conductors is prevented. The present apparatus features a knuckle comprised of a round sphere received in a surrounding socket. These components holding securely and yet permitting flexure. Rotation which would otherwise twist the conductors is prevented. Rotation is prevented by incorporating a fastening pin in the socket which extends into the sphere serving as a knuckle, and the sphere is cut with a lengthwise groove which limits flexure and prevents rotation, and thereby assures proper bending without rotation. This prevents twisting of the components.
The present apparatus is therefore summarized as an improved multiple knuckle and socket installation enabling flexure of an elongate oil tool. All the components are axially hollow with transverse bulkheads at spaced locations. The bulkheads receive feedthroughs for the conductors. Moreover, the feedthroughs provide pressure fluid isolation at the bulkhead. The bulkhead directs the cabling into closed chambers which are filled with protective oil. The oil is pressurized to the level attained by the ambient conditions downhole, and an increase above this level is insured by incorporating a pressure balanced piston biased by a spring to assure proper compensation. This excludes intrusion of fluids from the well borehole and thereby protects the internal working parts of the system.